Did you fill up the other three tire with air. Sometime it takes a little bit for that light to go out, atleast it did in my Optima SX that I had. The temperature probably has something to do with it, when I was stationed at Fort Drum my tires were low on pressure, it seemed like all the time an the fluctuation in temp was the culprit.
Make sure you fill your spare tire, those tires leak air.